Isobutanol production by combined and metabolic engineering

The production of the biofuel, isobutanol, in faces limitations due to alcohol toxicity, product inhibition, product recovery, and long-term industrial feasibility. Here we demonstrate an approach of combining both with metabolic engineering to produce isobutanol. The production of α-ketoisovalerate (KIV) was conducted through CRISPR mediated integration of the KIV pathway in bicistronic design (BCD) in and inhibition of competitive valine pathway using CRISPRi technology. The subsequent conversion to isobutanol was carried out with engineered enzymes for 2-ketoacid decarboxylase (KIVD) and alcohol dehydrogenase (ADH). For the production of KIV and subsequent production of isobutanol, this two-step serial approach resulted in yields of 56% and 93%, productivities of 0.62 and 0.074 g L h, and titers of 5.6 and 1.78 g L, respectively. Thus, this combined biosynthetic system can be used as a modular approach for producing important metabolites, like isobutanol, without the limitations associated with production using a consolidated bioprocess.